Peptide-loaded nanoparticles and radionuclide imaging for individualized treatment of myocardial ischemia

Polymeric Nanosystems Applied for Metal-Based Drugs and Photosensitizers Delivery: The State of the Art and Recent Advancements

Nanotechnology-based approaches for targeting the delivery and controlled release of metal-based therapeutic agents have revealed significant potential as tools for enhancing the therapeutic effect of metal-based agents and minimizing their systemic toxicities. In this context, a series of polymer-based nanosized systems designed to physically load or covalently conjugate metal-based therapeutic agents have been remarkably improving their bioavailability and anticancer efficacy. Initially, the polymeric nanocarriers were applied for platinum-based chemotherapeutic agents resulting in some nanoformulations currently in clinical tests and even in medical applications. At present, these nanoassemblies have been slowly expanding for nonplatinum-containing metal-based chemotherapeutic agents. Interestingly, for metal-based photosensitizers (PS) applied in photodynamic therapy (PDT), especially for cancer treatment, strategies employing polymeric nanocarriers have been investigated for almost 30 years. In this review, we address the polymeric nanocarrier-assisted metal-based therapeutics agent delivery systems with a specific focus on non-platinum systems; we explore some biological and physicochemical aspects of the polymer–metallodrug assembly. Finally, we summarize some recent advances in polymeric nanosystems coupled with metal-based compounds that present potential for successful clinical applications as chemotherapeutic or photosensitizing agents. We hope this review can provide a fertile ground for the innovative design of polymeric nanosystems for targeting the delivery and controlled release of metal-containing therapeutic agents.

Nanomaterials: A Promising Therapeutic Approach for Cardiovascular Diseases

Cardiovascular diseases (CVDs) are a primary cause of death globally. A few classic and hybrid treatments exist to treat CVDs. However, they lack in both safety and effectiveness. Thus, innovative nanomaterials for disease diagnosis and treatment are urgently required. The tiny size of nanomaterials allows them to reach more areas of the heart and arteries, making them ideal for CVDs. Atherosclerosis causes arterial stenosis and reduced blood flow. The most common treatment is medication and surgery to stabilize the disease. Nanotechnologies are crucial in treating vascular disease. Nanomaterials may be able to deliver medications to lesion sites after being infused into the circulation. Newer point-of-care devices have also been considered together with nanomaterials. For example, this study will look at the use of nanomaterials in imaging, diagnosing, and treating CVDs.

Radioactive polymeric nanoparticles for biomedical application

Nowadays, emerging radiolabeled nanosystems are revolutionizing medicine in terms of diagnostics, treatment, and theranostics. These radionuclides include polymeric nanoparticles (NPs), liposomal carriers, dendrimers, magnetic iron oxide NPs, silica NPs, carbon nanotubes, and inorganic metal-based nanoformulations. Between these nano-platforms, polymeric NPs have gained attention in the biomedical field due to their excellent properties, such as their surface to mass ratio, quantum properties, biodegradability, low toxicity, and ability to absorb and carry other molecules. In addition, NPs are capable of carrying high payloads of radionuclides which can be used for diagnostic, treatment, and theranostics depending on the radioactive material linked. The radiolabeling process of nanoparticles can be performed by direct or indirect labeling process. In both cases, the most appropriate must be selected in order to keep the targeting properties as preserved as possible. In addition, radionuclide therapy has the advantage of delivering a highly concentrated absorbed dose to the targeted tissue while sparing the surrounding healthy tissues. Said another way, radioactive polymeric NPs represent a promising prospect in the treatment and diagnostics of cardiovascular diseases such as cardiac ischemia, infectious diseases such as tuberculosis, and other type of cancer cells or tumors.

KSNM60 in Cardiology: Regrowth After a Long Pause

The Korean Society of Nuclear Medicine (KSNM) is celebrating its 60th anniversary in honor of the nuclear medicine professionals who have dedicated their efforts towards research, academics, and the more comprehensive clinical applications and uses of nuclear imaging modalities. Nuclear cardiology in Korea was at its prime time in the 1990s, but its growth was interrupted by a long pause. Despite the academic and practical challenges, nuclear cardiology in Korea now meets the second leap, attributed to the growth in molecular imaging tailored for many non-coronary diseases and the genuine values of nuclear myocardial perfusion imaging. In this review, we describe the trends, achievements, challenges, and perspectives of nuclear cardiology throughout the 60-year history of the KSNM.

Biological Safety and Biodistribution of Chitosan Nanoparticles

The effect of unmodified chitosan nanoparticles with a size of ~100 nm and a weakly positive charge on blood coagulation, metabolic activity of cultured cardiomyocytes, general toxicity, biodistribution, and reactive changes in rat organs in response to their single intravenous administration at doses of 1, 2, and 4 mg/kg was studied. Chitosan nanoparticles (CNPs) have a small cytotoxic effect and have a weak antiplatelet and anticoagulant effect. Intravenous administration of CNPs does not cause significant hemodynamic changes, and 30 min after the CNPs administration, they mainly accumulate in the liver and lungs, without causing hemolysis and leukocytosis. The toxicity of chitosan nanoparticles was manifested in a dose-dependent short-term delay in weight gain with subsequent recovery, while in the 2-week observation period no signs of pain and distress were observed in rats. Granulomas found in the lungs and liver indicate slow biodegradation of chitosan nanoparticles. In general, the obtained results indicate a good tolerance of intravenous administration of an unmodified chitosan suspension in the studied dose range.

Nanotechnologies for early diagnosis, in situ disease monitoring, and prevention

Nanotechnology is an enabling technology with great potential for applications in stem cell research and regenerative medicine. Fluorescent nanodiamond (FND), an inherently biocompatible and nontoxic nanoparticle, is well suited for such applications. We had developed a prospective isolation method using CD157, CD45, and CD54 to obtain lung stem cells. Labeling of CD45⁻CD54⁺CD157⁺ cells with FNDs did not eliminate their abilities for self-renewal and differentiation. The FND labeling in combination with cell sorting, fluorescence lifetime imaging microscopy, and immunostaining identified transplanted stem cells allowed tracking of their engraftment and regenerative capabilities with single-cell resolution. Time-gated fluorescence (TGF) imaging in mouse tissue sections indicated that they reside preferentially at the bronchoalveolar junctions of lungs, especially in naphthalene-injured mice. Our results presented in Subchapter 1.1 demonstrate not only the remarkable homing capacity and regenerative potential of the isolated stem cells, but also the ability of finding rare lung stem cells in vivo using FNDs.

The topical use of antiretroviral-based microbicides, namely of a dapivirine ring, has been recently shown to partially prevent transmission of HIV through the vaginal route. Among different formulation approaches, nanotechnology tools and principles have been used for the development of tentative vaginal and rectal microbicide products. Subchapter 1.2 provides an overview of antiretroviral drug nanocarriers as novel microbicide candidates and discusses recent and relevant research on the topic. Furthermore, advances in developing vaginal delivery platforms for the administration of promising antiretroviral drug nanocarriers are reviewed. Although mostly dedicated to the discussion of nanosystems for vaginal use, the development of rectal nanomicrobicides is also addressed.

Infectious diseases are currently responsible for over 8 million deaths per year. Efficient treatments require accurate recognition of pathogens at low concentrations, which in the case of blood infection (septicemia) can go as low as 1 mL^–1. Detecting and quantifying bacteria at such low concentrations is challenging and typically demands cultures of large samples of blood (∼1 mL) extending over 24–72 h. This delay seriously compromises the health of patients and is largely responsible for the death toll of bacterial infections. Recent advances in nanoscience, spectroscopy, plasmonics, and microfluidics allow for the development of optical devices capable of monitoring minute amounts of analytes in liquid samples. In Subchapter 1.3 we critically discuss these recent developments that will, in the future, enable the multiplex identification and quantification of microorganisms directly on their biological matrix with unprecedented speed, low cost, and sensitivity.

Radiolabeled nanoparticles (NPs) are finding an increasing interest in a broad range of biomedical applications. They may be used to detect and characterize diseases, to deliver relevant therapeutics, and to study the pharmacokinetic/pharmacodynamic parameters of nanomaterials. The use of radiotracer techniques in the research of novel NPs offers many advantages, but there are still some limitations. The binding of radionuclides to NPs has to be irreversible to prevent their escape to other tissues or organs. Due to the short half-lives of radionuclides, the manufacturing process is time limited and difficult, and there is also a risk of contamination. Subchapter 1.4 presents the main selection criteria for radionuclides and applicable radiolabeling procedures used for the radiolabeling of various NPs. Also, an overview of different types of NPs that have so far been labeled with radionuclides is presented.

Ventricular wall biomaterial injection therapy after myocardial infarction: Advances in material design, mechanistic insight and early clinical experiences

Intramyocardial biomaterial injection therapy for myocardial infarction has made significant progress since concept initiation more than 10 years ago. The interim successes and progress in the first 5 years have been extensively reviewed. During the last 5 years, two phase II clinical trials have reported their long term follow up results and many additional biomaterial candidates have reached preclinical and clinical testing. Also in recent years deeper investigations into the mechanisms behind the beneficial effects associated with biomaterial injection therapy have been pursued, and a variety of process and material parameters have been evaluated for their impact on therapeutic outcomes. This review explores the advances made in this biomaterial-centered approach to ischemic cardiomyopathy and discusses potential future research directions as this therapy seeks to positively impact patients suffering from one of the world's most common sources of mortality.

Protective roles of bioactive peptides during ischemia-reperfusion injury: From bench to bedside

Ischemia-reperfusion (I/R) is a well-known pathological condition which may lead to disability and mortality. I/R injury remains an unresolved and complicated situation in a number of clinical conditions, such as cardiac arrest with successful reanimation, as well as ischemic events in brain and heart. Peptides have many attractive advantages which make them suitable candidate drugs in treating I/R injury, such as low toxicity and immunogenicity, good solubility property, distinct tissue distribution pattern, and favorable pharmacokinetic profile. An increasing number of studies indicate that peptides could protect against I/R injury in many different organs and tissues. Peptides also face several therapeutic challenges that limit their clinical application. In this review, we present the mechanisms of action of peptides in reducing I/R injury, as well as further discuss modification strategies to improve the functional properties of bioactive peptides.

Radiolabelled Polymeric Materials for Imaging and Treatment of Cancer: Quo Vadis?

Owing to their tunable blood circulation time and suitable plasma stability, polymer-based nanomaterials hold a great potential for designing and utilising multifunctional nanocarriers for efficient imaging and effective treatment of cancer. When tagged with appropriate radionuclides, they may allow for specific detection (diagnosis) as well as the destruction of tumours (therapy) or even customization of materials, aiming to both diagnosis and therapy (theranostic approach). This review provides an overview of recent developments of radiolabelled polymeric nanomaterials (natural and synthetic polymers) for molecular imaging of cancer, specifically, applying nuclear techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Different approaches to radiolabel polymers are evaluated from the methodical radiochemical point of view. This includes new bifunctional chelating agents (BFCAs) for radiometals as well as novel labelling methods. Special emphasis is given to eligible strategies employed to evade the mononuclear phagocytic system (MPS) in view of efficient targeting. The discussion encompasses promising strategies currently employed as well as emerging possibilities in radionuclide-based cancer therapy. Key issues involved in the clinical translation of radiolabelled polymers and future scopes of this intriguing research field are also discussed.

Nanomaterials for In Vivo Imaging

In vivo imaging, which enables us to peer deeply within living subjects, is producing tremendous opportunities both for clinical diagnostics and as a research tool. Contrast material is often required to clearly visualize the functional architecture of physiological structures. Recent advances in nanomaterials are becoming pivotal to generate the high-resolution, high-contrast images needed for accurate, precision diagnostics. Nanomaterials are playing major roles in imaging by delivering large imaging payloads, yielding improved sensitivity, multiplexing capacity, and modularity of design. Indeed, for several imaging modalities, nanomaterials are now not simply ancillary contrast entities, but are instead the original and sole source of image signal that make possible the modality's existence. We address the physicochemical makeup/design of nanomaterials through the lens of the physical properties that produce contrast signal for the cognate imaging modality-we stratify nanomaterials on the basis of their (i) magnetic, (ii) optical, (iii) acoustic, and/or (iv) nuclear properties. We evaluate them for their ability to provide relevant information under preclinical and clinical circumstances, their in vivo safety profiles (which are being incorporated into their chemical design), their modularity in being fused to create multimodal nanomaterials (spanning multiple different physical imaging modalities and therapeutic/theranostic capabilities), their key properties, and critically their likelihood to be clinically translated.

Radio-nanomaterials for biomedical applications: state of the art

The incorporation of radioactive isotope(s) into conventional nanomaterials can bring extra properties which are not possessed by original materials. The resulting radioactive nanomaterials (radio-nanomaterials), with added physical/chemical properties, can be used as important tools for different biomedical applications. In this review, our goal is to provide an up-to-date overview on these applications using radio-nanomaterials. The first section illustrates the utilization of radionanomaterials for understanding of in vivo kinetics of their parent nano-materials. In the second section, we focus on two primary applications of radio-nanomaterials: imaging and therapeutic delivery. With various methods being used to form radio-nanomaterials, they can be used for positron emission tomography (PET), single-photon emission computed tomography (SPECT), and multimodal imaging. Therapeutic isotopes-loading radio-nanomaterials can possess selective killing efficacy of diseased cells (e.g. tumor cells) and can provide promises for certain isotopes which are not able to be used in a conventional manner. The successful and versatile biomedical applications of radio-nanomaterials warrants further investigations of those materials and their optimizations can pave the way to future imaging guidable, personalized treatments in patients.

EMMPRIN-Targeted Magnetic Nanoparticles for In Vivo Visualization and Regression of Acute Myocardial Infarction

Inhibition of extracellular matrix (ECM) degradation may represent a mechanism for cardiac protection against ischemia. Extracellular matrix metalloproteinase inducer (EMMPRIN) is highly expressed in response to acute myocardial infarction (AMI), and induces activation of several matrix metalloproteinases (MMPs), including gelatinases MMP-2 and MMP-9. We targeted EMMPRIN with paramagnetic/fluorescent micellar nanoparticles conjugated with the EMMPRIN binding peptide AP-9 (NAP9), or an AP-9 scrambled peptide as a negative control (NAPSC). We found that NAP9 binds to endogenous EMMPRIN in cultured HL1 myocytes and in mouse hearts subjected to ischemia/reperfusion (IR). Injection of NAP9 at the time of or one day after IR, was enough to reduce progression of myocardial cell death when compared to Control and NAPSC injected mice (infarct size in NAP9 injected mice: 32%±6.59 vs Control: 46%±9.04 or NAPSC injected mice: 48%±7.64). In the same way, cardiac parameters were recovered to almost healthy levels (LVEF NAP9 63% ± 7.24 vs Control 42% ± 4.74 or NAPSC 39% ± 6.44), whereas ECM degradation was also reduced as shown by inhibition of MMP-2 and MMP-9 activation. Cardiac magnetic resonance (CMR) scans have shown a signal enhancement in the left ventricle of NAP9 injected mice with respect to non-injected, and to mice injected with NAPSC. A positive correlation between CMR enhancement and Evans-Blue/TTC staining of infarct size was calculated (R:0.65). Taken together, these results point to EMMPRIN targeted nanoparticles as a new approach to the mitigation of ischemic/reperfusion injury.

Nanoparticles for Cardiovascular Imaging and Therapeutic Delivery, Part 2: Radiolabeled Probes

Nanoparticulate imaging agents and therapeutics have proven to be valuable tools in preclinical cardiovascular disease research. Because of their distinct properties and significant functional versatility, nanoparticulate imaging agents afford certain capabilities that are typically not provided by traditional small molecule agents. This review is the second in a two-part series covering nanoparticulate imaging agents and theranostics. It highlights current examples of radiolabeled nanoparticulate probes in preclinical cardiovascular research and demonstrates their utility in applications such as blood pool imaging and molecular imaging of ischemia, angiogenesis, atherosclerosis, and inflammation. These agents provide valuable insight into the molecular and cellular mechanisms of cardiovascular disease and illustrate both the limitations and the significant potential of nanoparticles in diagnostic and therapeutic applications. Further technologic development to improve performance, address safety concerns, and fulfil regulatory obligations is required for clinical translation of these emergent technologies.

Nanoparticles for Cardiovascular Imaging and Therapeutic Delivery, Part 1: Compositions and Features

Imaging agents made from nanoparticles are functionally versatile and have unique properties that may translate to clinical utility in several key cardiovascular imaging niches. Nanoparticles exhibit size-based circulation, biodistribution, and elimination properties different from those of small molecules and microparticles. In addition, nanoparticles provide versatile platforms that can be engineered to create both multimodal and multifunctional imaging agents with tunable properties. With these features, nanoparticulate imaging agents can facilitate fusion of high-sensitivity and high-resolution imaging modalities and selectively bind tissues for targeted molecular imaging and therapeutic delivery. Despite their intriguing attributes, nanoparticulate imaging agents have thus far achieved only limited clinical use. The reasons for this restricted advancement include an evolving scope of applications, the simplicity and effectiveness of existing small-molecule agents, pharmacokinetic limitations, safety concerns, and a complex regulatory environment. This review describes general features of nanoparticulate imaging agents and therapeutics and discusses challenges associated with clinical translation. A second, related review to appear in a subsequent issue of JNM highlights nuclear-based nanoparticulate probes in preclinical cardiovascular imaging.

Improving Cerebral Blood Flow Through Liposomal Delivery of Angiogenic Peptides: Potential of ¹⁸F-FDG PET Imaging in Ischemic Stroke Treatment

Strategies to promote angiogenesis can benefit cerebral ischemia. We determined whether liposomal delivery of angiogenic peptides with a known biologic activity of vascular endothelial growth factor benefitted cerebral ischemia. Also, the study examined the potential of (18)F-FDG PET imaging in ischemic stroke treatment.

METHODS

Male Sprague-Dawley rats (n = 40) underwent 40 min of middle cerebral artery occlusion. After 15 min of reperfusion, the rats (n = 10) received angiogenic peptides incorporated into liposomes. Animals receiving phosphate-buffered solution or liposomes without peptides served as controls. One week later, (18)F-FDG PET imaging was performed to examine regional changes in glucose utilization in response to the angiogenic therapy. The following day, (99m)Tc-hexamethylpropyleneamine oxime autoradiography was performed to determine changes in cerebral perfusion after angiogenic therapy. Corresponding changes in angiogenic markers, including von Willebrand factor and angiopoietin-1 and -2, were determined by immunostaining and polymerase chain reaction analysis, respectively.

RESULTS

A 40-min period of middle cerebral artery occlusion decreased blood perfusion in the ipsilateral ischemic cortex of the brain, compared with that in the contralateral cortex, as measured by (99m)Tc-hexamethylpropyleneamine oxime autoradiography. Liposomal delivery of angiogenic peptides to the ischemic hemisphere of the brain attenuated the cerebral perfusion defect compared with controls. Similarly, vascular density evidenced by von Willebrand factor-positive staining was increased in response to angiogenic therapy, compared with that of controls. This increase was accompanied by an early increase in angiopoietin-2 expression, a gene participating in angiogenesis. (18)F-FDG PET imaging measured at 7 d after treatment revealed that liposomal delivery of angiogenic peptides facilitated glucose utilization in the ipsilateral ischemic cortex of the brain, compared with that in the controls. Furthermore, the change in regional glucose utilization was correlated with the extent of improvement in cerebral perfusion (r = 0.742, P = 0.035).

CONCLUSION

Liposomal delivery of angiogenic peptides benefits cerebral ischemia. (18)F-FDG PET imaging holds promise as an indicator of the effectiveness of angiogenic therapy in cerebral ischemia.